Method of high speed heating



July 10, 1962 N sB T 3,043,368

METHOD OF HIGH SPEED HEATING Original Filed Sept. 20, 1954 2 Sheets-Sheet 1 INVENTOR.

JOHN D. NESBI TT HIS ATTORN E July 10, 1962 J. D. NESBITT METHOD OF HIGH SPEED HEATING 2 Sheets-Sheet 2 Original Filed Sept. 20, 1954 a 43 vm 1\!.. E MU .w I R D. m N w n J 5 Y m B m Z United States Patent 3,043,368 METHOD OF HIGH SPEED HEATING John D. Nesbitt, Sylvania, Ohio, assignor, by mesne assignments, to Midland-Ross Corporation, Cleveland, Ohio, a corporation of Ohio Continuation of application Ser. No. 457,119, Sept. 20, 1954. This application Apr. 21, 1958, Ser. No. 731,848 1 Claim. (Cl. 158117.5)

This invention relates to a fuel heated forge furnace of the type wherein fuel and air are delivered to the furnace chamber tangentially to the refractory walls thereof to ignite and burn on the walls and constitute them a source of radiant heat for heating work in the chamber.

The heating of such chambers with pre-mix burners wherein fuel and air are thoroughly mixed for combustion before delivery to the furnace chamber places limitations on turndown of the firing rate, since it is important to avoid combustion within the refractory nozzle or port in the furnace lining for the purpose of extending the useful life of the furnace refractory lining. In the manufacture of such furnace linings with high temperature refractories, it is preferred to cast the furnace lining as a unitary piece, including the firing ports. Placement of mandrels in such ports to make them substantially tangential to the finished inner surface of the lining provides a very diflicult mandrel removal problem. To remove such mandrels for reuse, they should be tapered, and a taper with the maximum diameter at the inner surface of the lining allows the greatest range of turn-down in firing rate, but makes mandrel removal very difficult. This invention provides a most advantageous solution to these problems by application of nozzle mixing to the firing ports in a manner allowing increased range of turn-down even with reversed taper of mandrel, thus allowing use of a reverse tapered mandrel and easy mandrel removal from outside the furnace barrel, and provides a nozzle mixing firing system adaptable to oil or gas firing and well adapted for its intended purpose.

For a consideration of what I believe to be novel and my invention, attention is directed to the following portion of the specification and the drawings and claim thereof.

In the drawing:

FIG. 1 is a longitudinal vertical sectional view of a furnace embodying this invention.

'FIG. 2 is a transverse sectional view of the improved furnace. I

FIG. 3 is a sectional view of a firing assembly for the furnace.

FIG. 4 is an enlarged view of a portion of 'FIG. 2 showing a step in manufacture of the furnace.

The furnace comprises a refractory lined tunnel having a casing 13 and forming a cylindrical chamber which will ordinarily be supported by lateral arms 12 atop supporting pillars '14. The work pieces W to be heated are passed through the furnace chamber at a level which is substantially within the central portion of the heating chamber, and are supported on internally cooled supports 15.

The inner lining 16 of the tunnel 10 is formed by a castable refractory mix as a monolithic lining having fuel inlet ports 17 formed therein. These ports are formed in the castable by preplacing mandrels 18 into a form within the casing before pouring the castable. The mandrels are tapered for ease of removal toward the outside of the chamber, as shown in FIG. 4. It will be appreciated that removal toward the center of the chamber 10 would be ditlicult due to the tangential placelow pressure.

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ment of mandrels 18 and the curvature of the lining 16.

The firing system for the furnace comprises an air manifold 21 mounted on the casing 13 and having a connecting air supply pipe 22 at one end thereof to supply air for combustion to the manifold at a relatively A series of inserts 23 are supported on the combustion air manifold 21 and extend into the inlet ports 17 through sleeve guides 24 mounted on the casing 13. The inserts 23 are provided with apertures 25f0r' passing combustion air from the manifold 21 to the ports 17, and have a restricted flow lip at their discharge end. A series of fuel delivery nozzles 26 are passed throught the inserts 23 to deliver an axial stream of fuel to the combustion air stream within the ports 17 to form a nozzle mixing fuel supply for the firing ports. The fuel for the firing ports may .be gas from a gas supply pipe 27 delivered through a three-way selector valve 28 and a manifold 31 to the several fuel delivery nozzles. The fuel may also be liquid, and may be passed into a gas carrier stream by an atomizing spray nozzle 32 from a liquid, such as oil, in fuel supply pipe 33. The carrier stream for the oil may be air from a relatively high pressure air supply pipe 36, or may be fuel gas from supply pipe 27. Air for the oil carrier stream may be supplied at pressures of about one pound per square inch or more, depending primarily upon the degree of atomization of the liquid fuel desired. It is preferred to pass the carrier gas past spray nozzle 32 at a sufficiently high velocity to carry away the spray without substantial wetting of the wall of the fuel delivery nozzle 26.

The fuel delivery nozzle is removably secured to the sleeve 23 by a packing gland 34, and both the sleeve and the nozzle are mounted on a face 35 of the combustion air manifold 21 which is perpendicular to the line of travel of the fuel stream tangentially to the inner surface of the chamber 10.

In operation on oil firing, a carrier gas stream such as air is delivered through pipe 36, selector valve 28', manifold 31 and nozzles 26. Oil is atomized into the air stream by a spray-nozzle 32 and is carried by the stream through the discharge end of the sleeve 23 and the port tunnel 17. The tapered end of the nozzle 26 stream lines flow of gas at the point and provides finest oil atomization. The discharge lip of the sleeve 23 serves to reduce to a minimum oil wetting of the port tunnel 17 An unburned mixture is thus delivered to the inner surface of the lining 16 for combustion thereon.

To obtain proper combustion of the oil the discharge end of the nozzle should be between the apertures and the end of the sleeve 23, thus assuring the carrying of the oil into the furnace with a minimum of wetting of the port tunnel 17. This application is a continuation of application Serial No.'457,l19 filed September 20, 1954, now abandoned.

I claim:

The method of heating a high temperature furnace having annular refractory wall means defining a chamber of substantially cylindrical configuration and having a plurality of inlet port tunnels extending through the wall means and disposed substantially tangentially to the internal surface thereof comprising, in combination: de-

livering a stream of unaerated gaseous fuel to each inlet nel; suddenly re-expanding the contracted contiguous streams of fuel and air at a point closely downstream to the point of contraction to cause partial intermixing of the streams varying in degree with the rate of flow of the stream of fuel and air; and passing the partially intermixed streams of fuel and air from the point of re-expansion to the outlet of the tunnel without further expansion, thereby to prevent the partially intermixed streams from burning in the tunnel; passing the partially intermixed streams of fuel and air from the outlet of the tunnel into the chamber substantially tangentially to the inner surface of the annular wall means; igniting the partially intermixed streams of fuel and air by heat transfer from the annular wall means; and burning the ignited streams as they pass circumferentially around the inner surface of the annular wall means.

References Cited in the file of this patent UNITED STATES PATENTS ar h. 

